The subject condition is not sufficient, and the angle between EF and plane PBC is uncertain. According to the subject conditions, it can only be determined that P is on the vertical plane in AD, and the trajectory of P is on the circle with E as the center and PE=2 as the radius on the vertical plane in AD. Limit position, p can be on the bottom ABCD plane, EF, PBC and ABCD***, and the included angle between EF and PBC is 0.